After a surgical operation, living body tissues often adhere to one another to cause a pain or a functional disorder. Adhesion occurs as a serious problem especially in a field such as obstetrics and gynecology, digestive surgery, orthopedics, and cardiovascular surgery, and a severe case requires an operation to separate the adhesion. In addition, occurrence of an adhesion increases risk upon a re-operation of a primary disease. As a method for preventing the adhesion of living body tissues, there has been proposed a method for isolating an area with a possibility of occurrence of the adhesion using a membrane called an anti-adhesion material.
The anti-adhesion material is required to have properties as follows: having flexibility that allows itself to fit an affected part as a hydrated gel; being immediately absorbed by a living body after maintaining its shape in the living body for a certain period of time; causing only slight tissue reaction; and the like. As an anti-adhesion material satisfying the above-mentioned properties, there has been proposed an anti-adhesion material comprising a film containing gelatin (for example, Patent Documents 1 to 6). Gelatin is a polymer derived from a living body, and has an excellent biocompatibility and the like.
However, gelatin films, as they are, absorb water in a living body so as to swell greatly, or are degraded in a very short period of time so as to be deformed. For these reasons, there have been problems that the gelatin films are difficult to handle and fail to produce sufficient effects on prevention of adhesion. In order to solve the problems, Patent Documents 1 to 6 disclose that crosslinking of a film containing gelatin by a suitable method allows the film to have a suitable water-containing property and suitable degradation. For example, Patent Documents 1, 4, 5, and 6 disclose ultraviolet-crosslinking, and Patent Documents 2 and 3 disclose a chemical crosslinking agent used in a combination.
However, there has been a problem that an anti-adhesion material comprising an ultraviolet-crosslinked gelatin film may be deformed in a living body at an early stage of use, in spite of its high degree of crosslinking.
On the other hand, the method of using a chemical crosslinking agent has a problem of a residue of a crosslinking agent or generation of a by-product derived from the crosslinking agent upon degradation in a living body.
Patent Document 1: Japanese Kokai Publication No. Hei-11-47258
Patent Document 2: Japanese Kokai Publication No. Hei-11-279296
Patent Document 3: Japanese Kokai Publication No. 2000-212286
Patent Document 4: Japanese Kokai Publication No. 2003-62063
Patent Document 5: Japanese Kokai Publication No. 2004-209228
Patent Document 6: Japanese Patent No. 3517358